Our colleague Steven T. Dennis recently ate the Iowa Republican’s dust in a race to the Senate subway. He later managed to pin down the supersonic septuagenarian for a chat about his training regimen.

“I run four days a week, three miles a day,” Grassley shared of the habit that he adopted on New Year’s 1998.

His pre-dawn runs are such an open secret, in fact, that Grassley was only mildly surprised to find a crew of visiting chamber of commerce folks camped out in front of his house Wednesday morning. “Five of these business people showed at my townhouse … to run with me at 4 o’clock,” he said.

Grassley is so pumped about the upcoming ACLI Capital Challenge (May 16) — an annual charity run historically owned by Sen. Dick Lugar (R-Ind.) — that he invited the press to come witness his speed-demon cells for themselves.

“I’ve got a team entered in that, and you can come see me run,” Grassley said.

And if you still harbor false hopes of ambushing Grassley in the Senate tunnels, just know that he’s got his elevator-to-subway sprint down pat. “I’ve got this timed. … I actually got there four seconds earlier,” Grassley said of a recent disappearing act.